PROSPECTIVE MIXTURE RISK ASSESSMENT AND MANAGEMENT PRIORITIZATIONS FOR RIVER CATCHMENTS WITH DIVERSE LAND USES

Abstract

Ecological risk assessment increasingly focuses on risks from chemical mixtures and multiple stressors, because ecosystems are commonly exposed to a plethora of contaminants and non-chemical stressors. To simplify the task of assessing potential mixture effects we explored three land-use related chemical emission scenarios. We applied a tiered methodology to judge the implications of the emissions of chemicals from agricultural practices, domestic discharges and urban run-off in a quantitative model. Results showed land-use dependent mixture exposures, clearly discriminating downstream effects of land uses, with unique chemical 'signatures' regarding composition, concentration and temporal patterns. Associated risks were characterized in relation to the land use scenarios. Comparisons to measured environmental concentrations and predicted impacts showed relatively good similarity. The results suggest that the land uses imply exceedances of regulatory protective Environmental Quality Standards, varying over time in relation to rain events and associated flow and dilution variation. Higher-tier analyses using ecotoxicological effect criteria confirmed that species assemblages may be affected due to exposures exceeding no-effect levels, and that mixture exposure could be associated with predicted species loss under certain situations. The model outcomes can inform various types of prioritization to support risk management, including a ranking across land uses as a whole, a ranking on characteristics of exposure times and frequencies, and various rankings of the relative role of individual chemicals. Though all results are based on in silico assessments, the prospective land-use based approach applied in the present study yields useful insights for simplifying and assessing potential ecological risks of chemical mixtures and can therefore be useful for catchment management decisions. This article is protected by copyright. All rights reserved

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